The present invention relates to an extruder for mixing, homogenizing and extruding rubber materials, such as natural rubber and synthetic rubber.
A conventional extruder of this type, as shown in Japanese patent publication No. 56-53500 published on Dec. 19, 1981 and claiming priority from West German application No. P 22 35 784.2 filed on July 21, 1972, includes a casing forming a cylindrical bore that contains a rotatable screw which forms a spiral passage for rubber materials in the casing. A number of mixing pins radially extend through the casing, so that adjustable lengths of the pins project into the spiral passage. Some of the pins extend through a space in the casing formed for a heating or cooling medium. The thread of the screw is formed with notches for the pins to pass through when the screw rotates.
In a conventional extruder of the foregoing type, it is troublesome to adjust the projecting lengths of the pins, and the arrangement limits the volume of the space for the cooling medium. In addition, the medium may leak through seals around the pins.
It is a general object of the present invention to provide an extruder for rubber materials, which enables mixing means such as pins to be easily replaced to obtain the desired projecting lengths and intervals (pitch) depending on the type of the material being processed, and for easy inspection and repair.
It is another object of the invention to provide such an extruder which has a sufficient flow volume for a heating/cooling medium, without leakage of the medium.
It is a further object of the invention to provide such an extruder containing a spiral passage, wherein the undesirable resistance to the flow of the materials is reduced, thereby improving the mixing effect.